Earth-boring tools are used to form boreholes (e.g., wellbores) in subterranean formations. Such earth-boring tools include, for example, drill bits, reamers, mills, etc. For example, a fixed-cutter earth-boring rotary drill bit (often referred to as a “drag” bit) generally includes a plurality of cutting elements secured to a face of a bit body of the drill bit. The cutting elements are fixed in place when used to cut formation materials. A conventional fixed-cutter earth-boring rotary drill bit includes a bit body having generally radially projecting and longitudinally extending blades. During drilling operations, the drill bit is positioned at the bottom of a well borehole and rotated as weight-on-bit (WOB) is applied.
A plurality of cutting elements is positioned on each of the blades. The cutting elements commonly comprise a “table” of superabrasive material, such as mutually bound particles of polycrystalline diamond, formed on a supporting substrate of a hard material, such as cemented tungsten carbide. Such cutting elements are often referred to as “polycrystalline diamond compact” (PDC) cutting elements. The plurality of PDC cutting elements may be fixed within cutting element pockets formed in rotationally leading surfaces of each of the blades. Conventionally, a bonding material, such as a braze alloy, may be used to secure the cutting elements to the bit body.
For directional drilling of nonlinear borehole segments, the face aggressiveness (i.e., aggressiveness of the cutters disposed on the blades over the face of the bit body) is a significant feature in terms of acceptable performance of the bit, since it is largely determinative of how a given bit responds to sudden variations in bit load. Unlike roller cone bits, rotary drill bits employing the PDC cutters are very sensitive to load, which sensitivity is reflected in much steeper rate-of-penetration (ROP) versus WOB and torque-on-bit (TOB) versus WOB relationships. Such high WOB sensitivity causes problems in directional drilling. Adjustments may be made to the bit structure in order to increase drilling efficiency while reducing mechanical specific energy (MSE) (i.e., the amount of force required to remove a given volume of rock). In particular, specific structural adjustments may be made in order to affect response to WOB and Aggressiveness (“Mu” or μ), which in turn affect build-up-rate (BUR). Conventional methods to improve rotary drill bit face aggressiveness include adjustments to cutter densities, cutter back rakes, blade number and configurations, and, significantly, the addition of depth-of-cut control (DOCC) structures to the face of the drill bit, particularly within the cone region.
The Assignee of the present disclosure and application has developed and implemented various approaches to the use of DOCC structures, as disclosed, for example, in U.S. Pat. Nos. 6,298,930 and 6,460,631, assigned to the Assignee herein, the disclosure of each of which is incorporated herein in its entirety by this reference. As is appreciated by one of ordinary skill in the art, the placement of DOCC structures within the cone region, while effective, has proven somewhat difficult to implement in smaller diameter bits, and in bits with relatively blade small widths in the rotational direction, as measured between rotationally leading and trailing sides of the blades. Such bits may not offer enough blade material and, thus, strength, to accommodate an aperture formed in an axially leading surface of a blade for holding a DOCC element. Certain solutions have been proposed and implemented to address this issue, examples including embodiments of preformed blade components disclosed in U.S. Pat. No. 7,814,997, the disclosure of which is incorporated herein in its entirety by this reference. Such solutions, while effective in some situations, add to the manufacturing cost of a bit. Other solutions, such as forming DOC limiters in the material, such as matrix material, of a leading surface of a blade simultaneous with forming a bit body as disclosed in U.S. Pat. No. 8,141,665, the disclosure of which is incorporated herein in its entirety by this reference, present issues with exposure control of the DOC limiters as well as constraints on the material of the DOC limiter.